# plotting prime_pi

Maybe I am missing something really simple, but shouldn't one be able to plot prime_pi?

```
----------------------------------------------------------------------
| Sage Version 4.5.1, Release Date: 2010-07-19 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: plot(prime_pi(x),3,10)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/home/dept/finotti/<ipython console=""> in <module>()
/scratch/local/sage-4.5.1/local/lib/python2.6/site-packages/sage/functions/prime_pi.so in sage.functions.prime_pi.PrimePi.__call__ (sage/functions/prime_pi.c:1064)()
/scratch/local/sage-4.5.1/local/lib/python2.6/site-packages/sage/symbolic/expression.so in sage.symbolic.expression.Expression.__int__ (sage/symbolic/expression.cpp:4171)()
/scratch/local/sage-4.5.1/local/lib/python2.6/site-packages/sage/symbolic/expression.so in sage.symbolic.expression.Expression.n (sage/symbolic/expression.cpp:17042)()
TypeError: cannot evaluate symbolic expression numerically
```

It seems wot work fine with real input

```
sage: prime_pi(pi)
_3 = 2
sage: prime_pi(1020.312788)
_4 = 171
```

Thanks,

Luis